loudspeakers. Options are to use the two remaining magnetic tracks for subwoofer signals and/or split
(dual channel) surrounds.
The 35 mm format was modified during the 1950’s to handle four magnetic tracks: three screen
channels and a single surround channel. At the same time, the standard monophonic variable area
optical track was maintained. Figures
and B show the channel layout for both 70 mm and 35 mm
magnetic standards. At present, the 35 mm magnetic standard is no longer in general use.
A. 70
m m
STRIPING
0.35
m m
Figure 1. 70mm six-track magnetic format (A); 35mm four-track magnetic format (B)
Figure 2A. 35mm Dolby Stereo Optical format
3
